-LRB- CNN -RRB- -- John Cossman 's friends call him cancer 's iron man . He 's had more than 90 radiation treatments and 200 chemo treatments since being diagnosed with head and neck cancer eight years ago .

The cancer has spread to his right lung , his right arm and his brain . Four years ago , he ran out of treatment options -- every available form of chemo had been used .

If he wanted to live , he 'd have to enter clinical trials .

`` How long do I have here ? '' he asked his doctor .

`` With treatment , two years , '' the doctor responded . `` Without treatment , six months . ''

Now , Cossman , 61 , is sitting in a doctor 's office , ready to undergo a CT scan that will determine if his cancer is being kept in check . He 's on his fourth clinical trial .

Three times , he 's heard bad news . He tries not to think about that as he slides into the giant machine that envelopes his body .

He thinks instead of his wife and 13-year-old daughter , adopted from China . Life offers too much to give in .

`` I will know when there 's not a whole helluva lot of time left . And I do n't feel that way right now . ... If what I 'm doing can help somebody down the line , then it 's worthwhile . ''

Holding disease at bay

Cossman is one of 16 patients with progressive forms of cancer currently taking part in a study of a developmental drug by the Cambridge , Massachusetts-based Cerulean Pharma . The company hopes to add another 20 patients to the trial in laboratories in Arizona , California and New Mexico .

The test drug is in the second phase of a three-phase process that takes years before the Food and Drug Administration even considers whether to bring the drug to market .

Cossman is one of the tens of thousands of people worldwide enrolled in drug trials . According to ClinicalTrials.gov , there are more than 96,500 trials under way in 174 countries . Cossman learned of drug trials through his oncologist -- `` otherwise , I 'd know nothing about them . ''

He wants to make others `` aware of head and neck cancer , and that clinical trials are available , '' he says . `` People need to be aware , though , that they are rolling the dice . ''

In this case , the chemotherapy drug , known as CRLX101 , is placed inside nanoparticles -- tiny particles just slightly bigger than molecules -- that are delivered intravenously every two weeks to patients .

The hope is that the nanoparticles target the cancer and release chemotherapy inside the tumors while shielding healthy tissue from the toxicity of chemo , says Oliver Fetzer , the president and CEO of Cerulean .

By doing that , the drug homes in on the tumors and , at the same time , patients can maintain a decent quality of life . `` You want to see how long you can actually hold the disease at bay , '' Fetzer says .

Adds John Ryan , Cerulean 's chief medical officer : `` The true measure of success in oncology is extending the length of time someone stays alive . ''

Yet this drug is far from market . The FDA can put a stop to a clinical trial at any moment if unexpected safety issues arise .

`` We keep in touch with the FDA constantly throughout the clinical trial , '' Ryan says . `` There 's a constant interchange with the FDA , particularly with respect to the safety of the drug and anything unexpected . ''

It takes about nine years for an oncology drug to go through the necessary clinical studies to FDA approval , said Dr. Kenneth Kaitin , director of The Tufts Center for the Study of Drug Development , an independent nonprofit research group .

According to a 2007 study by the center , a drug company spends about $ 1.3 billion per approved product , a figure that includes costs of failed test drugs .

When the test drug is for cancer , the patients have very aggressive forms . Success is often measured in small steps .

`` What you 're normally looking at in this patient population , if you can keep it at bay for two months , you are actually doing quite well , because the patients are so far along '' with cancer , says Fetzer . `` It 's a rule of thumb at best , because every disease is different , every patient is different . ''

' I went through every type of chemo '

It started with a lump in his throat eight years ago . Cossman thought it would go away . His doctor diagnosed it as head and neck cancer -- a surprise to Cossman because he 's never been a heavy drinker or smoker .

He underwent 36 radiation and chemo treatments over 2 1/2 months . He survived on a feeding tube for six months .

The next three years would be cancer free . But in June 2005 , a tumor popped up in his right lower lung . Chemo and radiation began again . The tumor was eliminated , yet a spot showed up again about a year later .

`` You get to a point where they ca n't radiate the lung any more . ''

He still has breathing problems from the radiation to his lung . One chemo treatment clogged up his tear ducts . Another created a rash all over his body .

`` By June 2006 , '' he says , `` I went through every type of chemo that 's been approved for head and neck cancer . The chemo would either stop working or the side effects would be more detrimental to my health . ''

His option : Die or enter clinical trials .

The first study kept his tumors -- by that time he had four -- in check for about five months . To remain in a trial , tumor growth has to be limited to 20 percent . A scan showed 22 percent growth .

`` You ca n't immediately go from one study to another . You have to be washed out for 30 days of chemicals and radiation . ''

In his second study , he developed a tumor on his right arm .

He soon was having vision problems and started losing his hair .

The man who had already endured so much was diagnosed with a brain tumor . In December , he underwent surgery to remove it .

His third study earlier this year did not work . `` You hold your breath , hoping that it 's working . Then , when the CT scan comes back and it shows the tumors are growing , it 's really frustrating . ''

`` Do I get depressed ? Yes . But do I want to give up ? No , '' he says .

So Cossman entered his fourth study this summer , the trial by Cerulean Pharma .

Fighting on

Dressed in a medical gown , Cossman awaits the CT scan . He 's gently glided into the large tube . The tests take just a few minutes .

He does n't look for sympathy . He has no complaints about what he 's been dealt . In fact , he celebrates life because `` it 's been good to me . ''

His little girl was 5 when he was diagnosed . She 's now 13 .

He says far too few cancer patients who could be eligible for trials are aware of them . He wants others who are suffering to be more proactive -- to ask their doctors about all their options .

Slowly , he emerges from his CT scan . The waiting for results begins .

He heads home . He tries not to get his hopes up . His phone rings after a few hours . On the other end of the line , his doctor delivers the best news he 's had in more than a year .

His cancer has grown at a rate of 11 percent , enough to remain on the study .

Yet the good news is only temporary .

A few weeks later , blood shows up in Cossman 's bladder and a new tumor is found on his back . His doctor advises getting him off the study . Cossman hopes to enter a new one soon .

`` You 're always on a roller-coaster when you have cancer . You have some successes and a lot of failures . ''

Does he still have the fight to live ?

`` Definitely , '' he says .

CNN 's Jarrett Bellini contributed to this report .

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John Cossman has been battling cancer for eight years

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He turned to clinical trials to stay alive after regular treatment options ran out

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He underwent his fourth clinical study this summer ; he 's one of 16 people in the study

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Before FDA approval , a drug goes through yearslong testing